1. Field of the Present Invention
The present invention relates to a synthetic method for making thiophenols from phenols.
2. Description of the Prior Art
It has been reported that the rearrangement of diaryl thionocarbonates to diaryl thiolcarbonates via the Schonberg rearrangement offered a way of converting phenols to thiophenols (J. of the Amer. Chem. Soc., Vol. 77, pp. 2479-2482 (1955)). This reported procedure involved the preparation of symmetrical thionocarbonates by the action of thiophosgene on the phenols in two stages or, more conveniently, by treatment of a benzene solution of two moles of the phenol and one mole of thiophosgene with dry pyridine. This type of procedure was noted by M. S. Newman et al. in J. of the Amer. Chem. Soc., Vol. 31, pp. 3980-3984 (1966), but was indicated as being limited to a maximum yield possible of 50% with respect to conversion of a phenol to the corresponding thiophenol. Newman et al. instead proposed conversion of the phenol to the O -aryl dialkylthiocarbamate with its conversion to the S-aryl dialkylthiocarbamate and thence to the thiophenol.
More recently, various preparative methods for preparing thiophenols from phenols was described in Rodd's Chemistry of Carbon Compounds, Supplements to the 2nd Edition, Supplement to Vol. III, pp. 247-249 (1983). Among the routes that were mentioned was the transformation of the thionocarbonates to the thiolcarbonate using the Schonberg rearrangement, as well as a variation developed by Y. Araki et al. wherein the phenol is reacted with the compound of the formula ClC(S)R.